Magnetic nano-materials, as a kind of soft magnetic materials, have been widely applied in the fields of magnetic medium memory, magnetic resonance imaging, catalysts and so on. Magnetite is of great interest due to its good magnetic property, biocompatibility and low toxicity. Currently, the research on magnetite has been extended to the field of biological medicines, especially the targeted drug delivery, in which by an applied magnetic field, a targeted magnetic drug carrier containing nano-sized magnetite may enrich itself in lesion sites of an organism, thereby resulting in reduced exposure of normal tissues to the drug and decreased toxic and side effects, thus efficiently reducing the amount of the drug and improving the efficacy.
Currently, the preparation methods of magnetite mainly includes chemical co-precipitation, micro-emulsion, thermal decomposition, solvent thermal synthesis and the like. The co-precipitation method is the most commonly used in the magnetic particle synthesis. This method is easy to operate; however, the resulting particles have poor dispersity and tend to produce heterogeneous phase, thereby generating impure products and with a wide particle distribution. The micro-emulsion method results in magnetic nanoparticles with a well-controlled particle diameter; however, they often have good dispersity in an oil phase while tend to agglomerate in an aqueous phase, which limits its application in biology. As a result, there is still a challenge in synthesis of magnetite nanospheres with good dispersity, uniform particle diameter and controlled dimension in an aqueous phase.